Diazotype material



United States Patent 3,459,550 DIAZOTYPE MATERIAL Johannes Munder, Wieshaden-Biebrich, Siegfried Scheler, Wiesbaden-Schierstein, and Richard Brahm, Ingelheim, Germany, assignors to Keuffel & Esser Company, Hoboken, NJ. N0 Drawing. Filed June 15, 1966, Ser. No. 557,617 Claims priority, application Germany, June 19, 1965,

56,433 Int. Cl. G03c 1/54; C07c 113/04 US. Cl. 96-91 3 Claims ABSTRACT OF THE DISCLOSURE One-component diazotype material of improved light sensitivity includes a 2-alkylmercapto-4-alkyl amino alkylmercapto-S-alkoxy diazonium compound.

The present invention relates to light-sensitive diazonium compounds useful in the diazotype process and more particularly relates to the preparation of improved onecomponent diazotype material.

In the one-component diazotype process there is used, as is known, a material in which there is a light-sensitive coating on a coating support, said support being in the form of a sheet or a film and there being present in said light-sensitive coating a diazo compound capable of being decomposed by light from the blue to ultraviolet region and, as a rule, also one or more auxiliary substances such as wetting agents, stabilizers, dispersing agents, anti-oxidants and binders. After imagewise exposure of the diazotype material, development is effected with a developer which is a (generally aqueous) solution of an azo component or of a mixture of ditierent azo components, in which butter salts, and perhaps alkalis for the setting up of the optimum pH-value for the coupling reaction, are contained.

In this process there are normally used only those azo components which have great coupling energy, most frequently phloroglucinol or resorcinol. Thus, there is used for example a developer which contains resorcinol or acetoacetic ester derivatives, in order to obtain copies with brown azo dye images. For development into the copies with very dark, if possible black, dye images which are frequently preferred in practice, developers are generally used which contain phloroglucinol or a mixture of phloroglucinol and resorcinol.

Since weakly acid phloroglucinol developers are substantially more stable and therefore more suitable for practical use than alkaline phloroglucinol developers, preferably those aqueous phloroglucinol developers are used whose pH-v-alue is less than 7.5, in particular those with a pH-value around 6. This, however, has the consequence that in the process the number of diazo compounds which can be used in practice is restricted, since only those with comparatively high coupling energy are particularly useful. Diazo compounds with high coupling energy are known, but their sensitivity to light is small compared with the light-sensitivity of diazo compounds with lower coupling energy. Thus, in German Patent No. 881,446 a one-component diazotype material is described, the lightsensitive substance of which is a p-mercaptophenylidazonium salt with two alkoxy groups in p-position to each other on the phenyl nucleus. If this material contains an arylmercaptophenyldiazonium salt, it does possess high coupling energy, but its light-sensitivity is insuflicient. If it contains an alkylmercaptophenyldiazonium salt, then the material is very light-sensitive, but because of insufficient coupling tendency it is disadvantageous for a process using a one-components diazotype material.

From Belgian Patent No. 649,392, diazotype materials are known which contain as light-sensitive substance a phenyldiazonium salt substituted in the 2-, 4- and 5-positions, the substituents either being groups which are identical to each other in all three positions or groups difierent from each other, each of which is a N-heterocyclic group, or mercapto group, attached to the phenyl nucleus by the hetero atom; or instead of one of the aforesaid substituents, there is an ether group as substituent in the 2-position or in the 5-position, or in the 2 -position and the 5- position, while in the other positions there is one of the substituents stated above.

In the Belgian patent, some diazo compounds are described as particularly advantageous because of their high light-sensitivity. These are phenyldiazonium salts etherified in the 5-position and to which a substituent is attached in the 2-position and 4-position by means of a hereto atom. The Belgian patent also describes a process in which a one-component diazotype material is used which contains a diazo compound of the configuration just stated and in which the material, after exposure, is developed with an alkaline reacting developer.

One object of the invention is the preparation of onecomponent diazotype material with a phenyldiazonium salt, which, after exposure, may be developed with a developer the pH- value of which is less than 7.5.

Another object of the invention is a one-component diazotype material with a phenyldiazonium salt which has high light-sensitivity.

As the diazonium salt which serves as light-sensitive substance according to the invention, one or several compounds may be used which have the following general formula:

wherein:

R is alkyl, aryl, or aralkyl;

R is alkyl, cycloalkyl, aralkyl, or aryl; R is alkyl, cycloalkyl, aralkyl; and

X is an acid anion In the ether groups and mercapto groups of the diazonium compound according to the invention, as alkyl groups those are preferred which have up to ten carbon atoms, including the carbon atoms of any further substituents attached to the alkyl groups. Of the cycloalkyl groups, the cyclohexyl group and the methylcyclohexyl group are particularly useful. The aralkyl group has preferably not more than 15 carbon atoms, including those of any attached substituents.

The diazonium salt used may be a salt of any desired acid which is capable of forming a water-soluble salt with the diazonium base; in particular strong inorganic acids, such as sulphuric or hydrochloric acid, are eligible,

but phosphoric, fiuoboric or hexafiuophosphoric acid may also be used. The diazonium salts may also be present in the form of double salts which are formed with salts of a heavy metal, for example with zinc chloride, stannic chloride or cadmium chloride.

The diazo compounds to be used according to the invention bear, as ether group in the 5-position with reference to the diazonium group, for example a methylether, ethylether, n-propylether, isopropylether, n-butylether, isobutylether, tert.-butylether, benzylether or phenylether group. These ether groups may, if they have more than one carbon atom contain further substituents, for example one or several halogen, hydroxy, alkoxy, carboxyl, carbaminyl, alkoxycarbonyl, alkylmercapto, aralkylmercapto, arylmercapto, or amino radicals, the latter including alkylamino radicals and cyclic amino radicals as for example morpholino or pyrrolidino radicals.

The mercapto group in the 4-position with respect to the diazo group is for example a methylmercapto, ethylmercapto, n-propylmercapto, isopropylmercapto, n-butylmercapto, isobutylmercapto, tert-butylmercapto, cyclohexylmercapto, cyclopentylmercapto or benzylmercapto group; the mercapto groups themselves may also, if they contain more than one carbon atom, as stated above in the case of the ether group, be substituted by further substituents.

The mercapto group in the 2-position may for example be a methyl-mercapto, ethylmercapto, n-propyl-mercapto, isopropylmercapto, n-butylmercapto, isobutylmercapto, tert-butylmercapto, cyclohexylmercapto, cyclopentylmercapto, benzylmercapto or phenylmercapto group; these mercapto groups also may, if they contain more than one carbon atom, as stated above, themselves be substituted by further substituents.

In the process, the exposed diazotype material is developed with a developer, the pH-value of which is below 7.5. Preferably, a developer is used the pH-value of which is not more than 7 and not less than 5.

The support of the diazotype material to be used according to the invention may be non-transparent or weakly translucent, such as paper, cloth and glazed paper, or strongly translucent, such as coated or uncoated tracingpaper, or transparent, such as cellulose acetate, cellulose acetobutyrate and polyester films, or films consisting of other polymers or copolymers. When the support is of itself hydrophobic, as for example, cellulose acetate or polyester foils, the diazo compound is preferably introduced into a thin hydrophilic coating prepared by hydrolysis of ester groups present in the surface layer of the support.

The preferably aqueous sensitizing liquids which are used for the preparation of the one-component diazotype material according to the invention may contain, besides the said diazo compounds, the customary stabilizers such as citric acid, tartaric acid, boric acid, sulphosalicylic acid, sulphamic acid, naphthalenedisulphonic or naphthalenetrisulphonic acid (sodium salts), anti-oxidants such as thiourea, metal salts such as aluminum sulphate, binders such as gelatin, gum arabic, synthetic resin dispersions or silicate dispersions, and other additives.

The diazo compounds to be used are, in the course of their preparation, obtained in most cases in the form of their chlorides or in the form of the double salts of these chlorides with metal chlorides, in particular with zinc chloride, cadmium chloride or stannic chloride and are therefore generally used in this form for the preparation of the one-component diazotype material. Some of these diazo compounds may also be used in the form of their borofluorides or their hexafluorophosphates.

The diazo compounds to be used may be prepared from the corresponding ethers of 4-chloro-2-aminophenol, in which ethers the phenol group is etherified with a group which corresponds to one of the ether groups mentioned above. If the ether group is an alkylether group or an aralkylether group, these ethers are obtained from 4-chlorophenol by introduction of a nitro group into the o-position with respect to the hydroxyl group by nitration with nitric acid, followed by etherification of the phenolic hydroxyl group with the corresponding alkyl chloride or alkylbromide or a corresponding dialkylsulphate, and reduction of the nitro group to form the amino group.

If the ether group is an unsubstituted or substituted arylether group, the 4-chloro-2-aminophenylaryl ether is obtained by melting together of 2,5-dichloronitrobenzene with the corresponding hydroxy-aryl compound and potassium hydroxide followed by reduction of the nitro group. To prepare the diazo compounds, firstly the amino group of these 4-chloro-2-aminophenols etherified with the appropriate group is acetylated, a nitro group introduced into the p-position with respect to the acetylamino group by nitration, and deacetylation is then effected.

In cases where the two mercapto groups in the desired diazo compound are the same, it is advantageous to proceed by exchanging the amino group for chlorine by means of a Sandmeyer reaction and then exchanging both chlorine atoms of the thus obtained dichloronitrophenol ether for a 'suitable mercapto radical, e.g. by reaction with the potassium salt of the alkyhnercaptan or arylmercaptan concerned.

In cases where the two mercapto groups in the desired diazo compound are difierent from each other, it is expedient to proceed by exchanging the chlorine atom in the 4-position for a desired mercapto group, then replacing the primary amino group in the 2-position by a chlorine atom by means of a Sandmeyer reaction, and exchanging this chlorine atom for the desired mercapto group.

The nitro group of the nitrodimercaptophenol ether obtained in either case is then, e.g. by hydrogenation by means of hydrogen in the presence of a hydrogenation catalyst, reduced to form the amino group, which is then diazotized. The diazo compounds may for example be obtained in the form of a double salt by precipitation with zinc chloride or cadmium chloride.

The 2,4-dimercaptophenyl-diazonium salts etherified in their 5-position which are to be used according to the invention are very sensitive to the light from high-pressure or low-pressure mercury vapour lamps, carbon arc lamps and fluorescent tubes suitable for diazotype purposes which is usually used in diazotype processes. Thus, for example, the end of exposure in the case of diazotype papers sensitized with a diazo compound according to the invention is reached substantially more rapidly than in the case of the hitherto known one-component diazotype material of acceptable coupling speed. Diazotype material sensitized with such diazo compounds is also very well suited for observation of the end of exposure with the naked eye, it copying is efiected with light from one of the above-mentioned types of lamp.

Besides high light-sensitivity, these diazo compounds possess an exceptionally great coupling activity. A diazotype material sensitized with these new diazo compounds develops extraordinarily fast with weakly acid phloroglucinol developers (pH 5.9 to 6.2) and yields extremely high-contrast copies with strong, dark coloured azo dye images. The diazo-type material according to the invention is therefore an excellent one-component diazo-type material capable of wet-acid development. The azo dye images of the copies made do not bleed and do not show, or show only in very much lesser degree, the disadvantageous phenomena which, as is known, occur in the case of incomplete development. Nor do thus developed copies show any coloured background attributable to the formation of dye by the light-decomposition products. In the case of half-tone copies, e.g., in the case of copies of pencil originals, the clouding of the image background is in the same hue as the image.

In the following examples, one part by weight is 1 g. when 1 ml. is taken as one part by volume.

5 EXAMPLE 1 White photocopying paper, which is provided with a precoat consisting of finely divided silica and polyvmylacetate, is sensitized with a solution of Gum arabic parts by weight 0.5 Citric acid d 0.5 Sodium naphthalene-1,3,6-trisulphonate do 3.5 Double salt from 4,6-diethylmercapto-3-methoxybenzenediazonium chloride and zinc chloride do 1.8 Water parts by volume 100 Phloroglucinol parts by weight" 0.4 Sodium adipate do 2.0 Sodium benzoate do 2.4 Adipic acid do 0.2 Trisodium citrate (anhydrous) do 9.6 Sodium chloride do 5.7 Sodium alkylsulphonate as wetting agent do 0.15 Water parts by volume 100 The pH-value of the developer is about 6.

Immediately after application of the developer 11 qu1d, the developed copy shows a strong, slightly violet-tmged black image on a clear white background without bleeding.

The diazo compound used according to this example is prepared as follows:

4-chloro-2-acetylamino-anisole is nitrated and the thus obtained nitro compound (melting point 194-19 5 C. deacetylated and converted into 4,6-dichloro-3-mtro-amsole (melting point 77-79" C.) by exchanging the ammo group for chlorine by means of a Sandmeyer reactlon By reaction with ethylmercaptan (potassium salt), S-mtro- 2,4-diethylmercapto-anisole (melting point 76-78 C.) 1s obtained. The nitro group of this compound is reduced in a usual manner to form the amino group and this is converted into the corresponding diazonium group.

EXAMPLE 2 The same procedure is followed as in Example 1, but instead of the 1.8 g. of the double salt stated therein 1.9 parts by weight of the double salt from 6-n-butylmercapto 4 ethylmercapto 3 methoxy-benzenediazonium chloride and zinc chloride are used in the sensitizing liquid. A copy with a strong, neutral black image on a pure white background is obtained. The azo dye does not fade in the daylight.

The diazo compound used in obtained as follows:

4-chloro-5-nitro-2-acetylamino-anisole, which can be obtained in the manner described in Example 1, is deacetylated and reacted with n-butylmercaptan( potassium salt) to form 5-nitro-4-n-butylmercapto-2-amino-anisole (melting point 143-l45 C.). By replacement of the amino group by chlorine by means of a Sandmeyer reaction, 6-chloro-3-nitro-4-n-butylmercapto-anisole (melting point 8485 C.) is obtained, which is converted with ethylmercaptan (potassium salt) into 5-nitro-4-n-butylmercapto-2-ethylmercapto-anisole (melting point 74-75" C.). This compound is reduced to form the corresponding amine and the latter converted into the diazo compound.

6 EXAMPLE 3 A white photocopying paper of the kind commonly used in diazotype processes is coated with a solution of and dried. The light-sensitive side of a sheet of this diazotype paper is exposed in contact with a tracing paper on which there is a pencil drawing. Exposure is continued until a slight yellow colouration (and thus a small amount of diazo compound) remains in the parts of the copying coating which are in contact with the non-image areas of the drawing. The point in time at which the exposure must be ended can be observed very easily with the naked eye, by looking, during exposure, at the copy in the direction in which the exposure light is incident upon it and following the change of colour occurring in the light-sensitive coating. This point in time is reached very rapidly.

The latent diazotype copy thus obtained is developed by applying to its image side a coating of about 10 g./m. of a developer liquid which contains in 100 parts by volume of water Parts by weight Phloroglucinol 0.86 NaH PO .2H O 3.0 Na HPO l2H O 3.0

Sodium diisopropylnaphthalene-sulphonate as wetting agent 0.1

The pH-value of this developer is about 6.2. Immediately after application of the developer liquid, the developed copy shows a strongly black image on a uniformly clouded, grey coloured background, The azo dye in the clouded background has the same colour as that in the black portions of the image.

The diazo compound used according to this Example is prepared as follows:

4 chloro 5 nitro 2 amino-anisole(melting point 122l23 C.), which can be obtained in the manner described in Example 1, is reacted with n-butylmercaptan (potassium salt). The product thus obtained melts at 143-145 C. It is converted by means of a Sandmeyer reaction into 6 chloro 3 nitro 4 n-butylmercaptoanisole (melting point 8485 C.). Reaction of the latter with n-butylmercaptan (potassium salt) yields 5-nitro-2, 4-di-n-butylmercapto-anisole (melting point 5758 C.) the nitro group of which is, as usual, reduced to form the amino group, and the thus obtained amine then diazotised.

EXAMPLE 4 A transparentised paper of the kind commonly used as a support in diazotype processes is coated with a solution of Citric acid parts by weight 0.5 Saponine do 0.1 Triglycol do 2.5 Isopropanol parts by volume 10 Water do Double salt from 6-ethylmercapto-4-n-butylmercapto- 3 methoxy benzenediazonium chloride and zinc chloride parts by weight 1.9

and dried. A sheet of the diazotype material thus obtained is, as stated in Example 1, imagewise exposed, and the latent diazotype copy then developed with the developer liquid stated in Example 1.

Immediately after application of the developer liquid, a strongly black image on a clear background is obtained. The dyes formed in the image areas are substantially opaque to ultraviolet light, for which reason these copies are suitable as intermediate originals for the preparation of further copies on diazotype papers.

The diazo compound used in this example is obtained as follows:

4-chloro-5-nitro-2-amino-anisole, which can be obtained in the manner described in Example 1, is reatced with ethylmercaptan (potassium salt). The product thus obtained (melting point 164l65 C.) is converted into 6-chloro-3-nitro 4 ethylmercapto-anisole (melting point 112-l13 C.) by means of a Sandmeyer reaction, and then reacted with n-butylmercaptan (potassium salt). The 5-nitro-4-ethylmercapto-2-n-butylmercapto-anisole (melting point 8183 C.) thus obtained is reduced to form the corresponding amino compound and the latter diazotised in the usual manner.

EXAMPLE 5 White base paper of the kind commonly used in diazotype process is sensitised with a solution of Gum arabic parts by weight 0.5 Citric acid do 0.5 Sodium naphthalene-1,3,6-trisulphonate do 3.5 Double salt from 6-n-butylmercapto-4-(beta-dimethylamino) ethylmercapto 3 methoxy-benzenediazonium chloride and cadmium chloride (as acid salt) do 3.4 Water parts by volume 100 and dried.

A sheet of the thus obtained diazotype paper is imagewise exposed as in Example 1, and the latent diazotype copy then developed with the developer liquid stated in Example 1.

Immediately after application of the developer liquid, the developed copy shows a strongly violet image on a pure white background. The violet azo dye does not bleed.

The diazo compound which was used in this example can be prepared as follows:

6-chloro-3-nitro-4-n-butylmercapto-anisole, which was obtained in the manner described in Example 3, is reacted with beta-diethylaminoethylmercaptan (potassium salt), the thus obtained product (melting point 54-5 6 C.) reduced to form the corresponding amine and the latter then converted into the diazo compound in the usual manner.

EXAMPLE 6 The same procedure is followed as in Example 5, but with the difference that instead of the diazonium chloride double salt used therein an equimolecular amount of the double salt from 6-ethylmercapto-4-(beta-diethylamino)- ethylmercapto-3-meth0xy-benzene diazonium chloride and zinc chloride is used in the sensitizing liquid. In this case, too, a copy with strongly violet azo dye images on a white background is obtained.

The diazo compound used in this Example is prepared as follows:

6-chloro-3-nitro-4-ethylmercapto-anisole, which was obtained as described in Example 4, is reacted with betadiethyl-aminoethylmercaptan (potassium salt), the thus obtained 5-nitro-4-ethylmercapto-2-(beta diethylamino)- ethylmercapto-anisole (melting point 69-72 C.) reduced to form the corresponding amine and the latter converted into the diazo compound in the usual manner.

EXAMPLE 7 A transparent paper of the kind commonly used in diazotype processes is sensitized with a solution of Gum arabic parts by weight 0.5 Critric acid do 0.5 Sodium naphthalene-1,3,6-trisulphonate do 3.5

Double salt from 4,6-diethylmercapto-3-methoxybenzenediazonium chloride and zinc chloride do 3.6 Water parts by volume 100 and dried.

A sheet of the diaztoype material thus obtained is, as stated in Example 1, imagewise exposed, and the latent diazotype copy developed by applying to the image side a coating of about 10 g./m. of a developer liquid of the following composition:

Potassium adipate part by weight 5.7 Sodium benzoate do 2.3 Adipic acid do 0.1 Thiourea do 0.5 Cane Sugar do 0.5 Sodium diisopropylnaphthalenesulphonate do 0.2 1-phenylpyrazolone-(5)-carboxylic acid-(3) do 1.2 Water parts by volume The pH-value of the developer is 5.7.

Immediately after application of the developer liquid, the copy shows a strong, orange coloured image on a pure white background. The azo dye formed in the image areas is not permeable to ultra-violet light, for which reason this copy is very suitable as intermediate original for the preparation of further copies on diazotype paper.

If in the sensitising liquid of any of the Example 1 to 7 there is used instead of the diazonium chloride double salts named therein an equimolecular amount of prior art material such as the zinc chloride double salt of N- benzoylamino-2,S-diethoxybenzene diazonium chloride or of 4-(4'-methylphenyl)-mercapto-2,5-diethoxybenzeneTil azonium chloride or of 4-(4-methoxyphenyl)-2,5-diethoxybenzene diazonium chloride or of 4-N-methyl-N-cyclohexylamino 2,5 dichlorobenzene diazonium chloride, the point in time when these diazo compounds in the parts corresponding to the translucent portions of the original are completely exposed is reached much later than in Examples 1 to 7. The said diazo compounds are thus less light-sensitive than those according to the invention.

If, in the sensitizing liquid, there is used instead of the diazonium chloride double salts mentioned in Examples 1 to 6 an equimolar amount of the known Zinc chloride double salt of 4-N,N-dimethylamino-3-(4-chlorophenoxy)-6-chlorobenzene-diazonium chloride, the completion of exposure is then reached in the same time, but when the developer liquids mentioned in Examples 1 and 3 are used, a completely developed copy, which shows a black image on a white background, is not obtained until some time has elapsed. The said, known diazo compound therefore has less coupling activity than the diazo compound according to the invention. This is also the case when the developer mentioned in Example 7 is used; moreover, there is then obtained with the said, known diazo compound a copy in red color, i.e. with less covering power in regard to ultra-violet light than the orange colored copies obtainable according to the invention with the use of this developer.

EXAMPLE 8 A white photocopying paper of the kind commonly used in diazotype processes is sensitised with a solution of Gelatine parts by weight" 0.5

Tartaric acid do 0.3

Aluminium sulphate do 0.3 Double salt from 4,6-diethylmercapto 3 methoxybenzenediazonium chloride and zinc chloride Water parts by volume 100 and dried.

A sheet of this diazotype material is imagewise exposed as described in Example 1 and the latent diazotype copy then developed by applying to its image side a coating of about 10 g./m. of a developer liquid of the lowing composition:

fol-

The pH-value of the developer is 5.8.

Immediately after application of the developer liquid, the copy shows strong, blue-violet lines on a pure white background.

Copies of similar colour are obtained when, instead of the diazo compound used in this example, the diazo compounds named in the preceding Examples 2, 3, 4, 5 and 6 are used.

The above examples have been presented for the purpose of illustration and should not be taken to limit the scope of the present invention. It will be apparent that the described examples are capable of many variations and modifications which are likewise to be included within the scope of the present invention as set forth in the appended claims.

What is claimed is:

1. Diazotype material comprising a support bearing a composition comprising a light-sensitive diazonium compound having the general formula:

a l l 10 wherein R is alkyl of one to four carbon atoms;

R is alkyl of one to four carbon atoms;

R is (beta-diethylamino)-ethyl;

X is an acid anion.

2. Diazotype material according to claim 1 wherein said diazonium compound is 6-n-butylmercapto-4-(beta-diethylamino) -ethylmercapto-3-methoxy-benzene diazonium chloride CdCl 3. Diazotype material according to claim 1 wherein said diazonium compound is 6-ethylmercapto-4-(beta-diethylamino)-ethylmercapto-3-methoxy benzene diazonium chloride ZnCl References Cited UNITED STATES PATENTS 2,286,701 6/ 1940 Werner 96-91 3,311,475 3/1967 Van Loon et al 9691 3,407,066 10/ 1968 Mustacchi et al. 96-91 FOREIGN PATENTS 740,565 11/1955 Great Britain.

864,011 3 1961 Great Britain.

868,715 5/ 1961 Great Britain.

895,249 5/ 1962 Great Britain.

511,504 6/1952 Belgium. 6,406,974 12/ 1964 Netherlands.

NORMAN G. TORCHIN, Primary Examiner C. BOWERS, Assistant Examiner U.S. C1. X.R. 96-49; 260141 

